Description

This is a somewhat common crash that has occurred throughout the 4.17 release. Users have not provided any description of their actions when the crash occurred.

The callstack is similar to some old crashes fixed back in 4.10 ([Link Removed], [Link Removed]) although this one doesn't share the lines related to HotReload.

Source Context

1870       		// WARNING: for (TPair<UClass*, UClass*> OldToNewClass : InOldToNewClassMap) duplicated below 
 1871       		// to handle reconstructing actors which need to be reinstanced aftertheir owned components 
 1872       		// have been updated:
 1873       		for (TPair<UClass*, UClass*> OldToNewClass : InOldToNewClassMap)
 1874       		{
 1875       			UClass* OldClass = OldToNewClass.Key;
 1876       			UClass* NewClass = OldToNewClass.Value;
 1877       			check(OldClass && NewClass);
 1878       #if WITH_HOT_RELOAD
 1879 ***** 			check(OldClass != NewClass || GIsHotReload);
 1880       #else
 1881       			check(OldClass != NewClass);
 1882       #endif
Steps to Reproduce

1. select 'Reload' from the Asset Actions menu of the BP_ParentClassISMissingType.uasset in QAGame

Callstack
Assertion failed: OldClass && NewClass 
[File:D:\Build\++UE4+Release-4.17+Compile\Sync\Engine\Source\Editor\UnrealEd\Private\Kismet2\KismetReinstanceUtilities.cpp] [Line: 1878]

UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReplaceInstancesOfClass_Inner() [kismetreinstanceutilities.cpp:1880]
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReplaceInstancesOfClass() [kismetreinstanceutilities.cpp:1463]
UE4Editor_UnrealEd!UEditorEngine::HandlePackageReloaded() [editorengine.cpp:694]
UE4Editor_UnrealEd!TBaseUObjectMethodDelegateInstance<0,UEditorEngine,void __cdecl() [delegateinstancesimpl.h:858]
UE4Editor_CoreUObject!TBaseMulticastDelegate<void,enum EPackageReloadPhase,FPackageReloadedEvent * __ptr64>::Broadcast() [delegatesignatureimpl.inl:937]
UE4Editor_CoreUObject!ReloadPackages() [packagereload.cpp:481]
UE4Editor_UnrealEd!PackageTools::ReloadPackages() [packagetools.cpp:584]
UE4Editor_UnrealEd!PackageTools::ReloadPackages() [packagetools.cpp:424]
UE4Editor_ContentBrowser!FAssetContextMenu::ExecuteReload() [assetcontextmenu.cpp:1904]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,FAssetContextMenu,0,TTypeWrapper<void> __cdecl() [delegateinstancesimpl.h:327]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,FAssetContextMenu,0,void __cdecl() [delegateinstancesimpl.h:434]
UE4Editor_Slate!SMenuEntryBlock::OnClicked() [smenuentryblock.cpp:1051]
UE4Editor_Slate!SMenuEntryBlock::OnMenuItemButtonClicked() [smenuentryblock.cpp:1002]
UE4Editor_Slate!TMemberFunctionCaller<SMenuEntryBlock,FReply() [delegateinstanceinterface.h:165]
UE4Editor_Slate!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SMenuEntryBlock,FReply() [tuple.h:497]
UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SMenuEntryBlock,0,FReply __cdecl() [delegateinstancesimpl.h:327]
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() [delegatesignatureimpl.inl:537]
UE4Editor_Slate!SButton::OnMouseButtonUp() [sbutton.cpp:282]
UE4Editor_Slate!SMenuEntryButton::OnMouseButtonUp() [smenuentryblock.cpp:399]
UE4Editor_Slate!<lambda_1002768c627006711ef2f351a87ec0e7>::operator() [slateapplication.cpp:5199]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_1002768c627006711ef2f351a87ec0e7> >() [slateapplication.cpp:232]
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [slateapplication.cpp:5188]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [slateapplication.cpp:5690]
UE4Editor_Slate!FSlateApplication::OnMouseUp() [slateapplication.cpp:5670]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [windowsapplication.cpp:1718]
UE4Editor_Core!FWindowsApplication::DeferMessage() [windowsapplication.cpp:2161]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [windowsapplication.cpp:881]
UE4Editor_Core!FWindowsApplication::AppWndProc() [windowsapplication.cpp:721]
user32!UserCallWinProcCheckWow()
user32!DispatchMessageWorker()
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [windowsplatformmisc.cpp:1009]
UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:3151]
UE4Editor!GuardedMain() [launch.cpp:166]
UE4Editor!GuardedMainWrapper() [launchwindows.cpp:134]
UE4Editor!WinMain() [launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [exe_common.inl:253]
kernel32!BaseThreadInitThunk()
ntdll!RtlUserThreadStart()

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Fixed
ComponentUE - Gameplay - Blueprint Compiler
Affects Versions4.174.18
Target Fix4.19
Fix Commit3806963
Main Commit3967553
Release Commit3821202
CreatedOct 5, 2017
ResolvedDec 13, 2017
UpdatedApr 27, 2018